import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathFactory;

import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.params.BasicHttpParams;
import org.apache.http.params.HttpConnectionParams;
import org.apache.http.params.HttpParams;

import org.w3c.dom.Document;


public class updater {
    public static void main(String[] args) throws IOException {
		try{
			DefaultHttpClient httpclient = ClientMaker();
			HttpGet get = new HttpGet("http://w...content-available-to-author-only...r.com/path/to/Version.xml");
			HttpResponse response = httpclient.execute(get);
			InputStream in = response.getEntity().getContent();

			DocumentBuilderFactory domFactory = DocumentBuilderFactory.newInstance();
			DocumentBuilder builder = domFactory.newDocumentBuilder();
			Document doc = builder.parse(in);

			//Parse the Xml.
			XPathFactory factory = XPathFactory.newInstance();
			XPath xpath = factory.newXPath();
			XPathExpression expr = xpath.compile("//version/number/text()");
			String result = (String) expr.evaluate(doc, XPathConstants.STRING);
			System.out.println(result);

			File f = new File("C:\\Users\\Damien\\Documents\\Eclipse\\MyOutput\\bin\\Version.xml");
			in = new FileInputStream(f) ;
			doc = builder.parse(in);
			expr=xpath.compile("//version/number/text()");
			String result2 = (String) expr.evaluate(doc, XPathConstants.STRING);
			System.out.println(result2);


			if(Integer.parseInt(result) < Integer.parseInt(result2)){
				HttpGet get2 = new HttpGet("http://w...content-available-to-author-only...r.com/path/to/MyJar.jar"); 
				HttpResponse response2 = httpclient.execute(get2);
				InputStream in2 = response2.getEntity().getContent();
				File f2 = new File("C:\\Users\\Damien\\Documents\\Eclipse\\path\\to\\MyJar.jar");
				OutputStream fos = new FileOutputStream(f2);
				byte buf[] = new byte[1024];
				int len;
				while ((len = in2.read(buf)) > 0) {
					fos.write(buf, 0, len);
				}
				fos.close();
				in.close();
			}
			Process p = Runtime.getRuntime().exec("cmd.exe /C  javaw -jar C:\\Users\\Damien\\Documents\\Eclipse\\path\\to\\MyJar.jar");
			p.waitFor();
			p.destroy();
		}catch(Exception e){ e.printStackTrace(); }


	}

	public static DefaultHttpClient ClientMaker() {
		int connectiontimeout = 30000; // 1 second int sockettimeout = 1000;
		HttpParams httpparameters = new BasicHttpParams();
		HttpConnectionParams.setConnectionTimeout(httpparameters,
				connectiontimeout);
		HttpConnectionParams.setSoTimeout(httpparameters, connectiontimeout);
		DefaultHttpClient httpclient = new DefaultHttpClient(httpparameters);
		return httpclient;
	}

}